Art or process of liquefying and separating air.



J. F. PLACE.

A'RT 0R PROCESS OF LIQUEFYING AND SEPARATING'AIRL APPLICATION FILEDNOV.29| I907.-

Patented Aug. 31, 1915.

\ 1;. PlzAEE. AR T OR PROCESS OF- ILIQ'UEFYING AN-D SEPR-RYATIiliNG AIR.

APPLICATION FILED NOV. 29.1907.

17,152,044. Patented Aug. 31,1915.

2 S EET SHEET 2 5. 3922mm 1: 7 60 54 (3:1 ucnl'o:

, (g 5/ J0 G R "UNITED s'rA'r s PATENT OFFICE.

JAMES F. PLACE, OF GLEN RIDGE, JERSEY, ASSIGNOR TO AMERICAN AIRLIQUEFYING 00., A CORPORATION 01 NEW YORK.

ART 0R PROCESS OF LIQUEFYING AND S EPARAT ING AIR.

Specification of Letters Patent.

Patented Aug. 3 1, 191-5.

Application filed November 29, 1907. Serial No. 40%,244. I.

' the:constituent gases of air, to a greater or less degree.

One object is toreduce the cost of the production of liquid air, andcorrespondingly lessen the cost of its constituent gases-oxygen andnitrogen. U

In order that those skilled in the art may make use of my invention, Iwill describe the same as-illustrated by the accompanying drawings, inwhich Figure 1 is a diagrammatic view, showing the necessary mechanismused in preparation of the air for liquefaction by my process, namely,the air compressor and water cooler; quick-lime, calcium chlorid andcaustic potash drums for removing the moisture and carbonic-acid gasfrom the air; and the CO freezing drum for freezing out furthermoisture, and aiding the thermal interchanger in reducing thetemperature of the air.. Fig.

- 2 is a View in vertical section of my thermal interchang'er, andsubmerged air-liquefying condenser and its accessories, used in availingof my art or process.

In my invention, I utilize the latent heat of vaporization required byliquid air at substantially atmospheric pressure, to cool and liquefyair while at or above. its critical pressure when there is no latentheat of condensation given out to neutralize refrigeration and retardliquefaction. It is well known that the critical pressure of air is 39atmospheres, and its critical temperature is 220 F. It will condense toa liquid at.

220 F., if-it be compressed to 39 atmospheres; and it will liquefy t alower com; pression if cooled to a lower temperature,'

or at atmospheric pressure if cooled," to

--3l2.6 F.; but no amount of compression.

will cause liquefaction unless it be cooled to its criticaltemperature,- namely,-220 F.

the submerged condenser.

If compressed to 39 atmospheres and cooled, to 220' F., its density thenas a gas is identical with its-density as a liquid; and with theslightest lowering of the temperature then, its change of state from agas to a liquid (if the pressure is maintained) is instantaneous, andthere can be no latent heat of condensation, as there is practically nofurther contraction,

By my process I compress air to about 4:5

atmospheres (647 lbs. gage) and liquefy all of the air compressed,without any reduction of pressure. It is liquefied in a highpressurecondenser, which is kept submerged in liquefied air of substantiallyatmospheric pressure, and after liquefaction it is sub- ,cooled as aliquid before release from pressure, until it is about the sametemperature ofthe low-pressure liquid air surrounding the-condenser, or313 F. Afterward it is released from pressure (as a sub-cooled,/

liquid) and delivered to the insulated reservoir which surroundsthecondenser, .(thus replenishing the evaporating liquid-charge therein) toliquefy and'sub-cool new and sun: cessivecharges of cooled compressedair in The latent heatof vaporization required by liquid air atatmospheric pressure is about 120 B. T. U. per pound; and this, with thecooling effect of the vapor of the evaporated liquid (as it passesthrough the thermal interchanger and absorbs heat from the incomingcompressed air unitl it'rises from 313 F. to normal temperature), is allutilized.

I will nowdescribe my art or process, and

in doing so will refer; to the mechanism I preferably make use of, asillustrated in the accompanying drawings, in which similar referencenumerals refer to similar parts;

throughout.

' At 1 in Fig. 1 I show' an ordinary 3-stage air compressor, or acompressor capable of compressing air to say about 50 atmos pheres,having the water cooler 2. This compressor is supplied with air atthesuction inlet 3, and suction pipe 4, which air. is drawn through thequick lime in the drum 1 v5 for'the purpose of absorbing the carbonicacid gas in the'air. The air after compression to about '45 atmospheres(or say 647 'lbs. gage) is delivered through pipe 6 to the calciumchlorid drum 7, and passed through the charges 8 of lump calciumchlorid; and'thence through pipe 9 to the caustic potash drum 10, andthrough similar charges 11, of broken caustic potash. The subjection ofthe compressed air to this purifying treatment usually removes everytrace of CO gas in the air and will reduce the moisture of the air toabout 10% saturation; The air is then passed through pipe 12 into what Icall the pre-cooler .(24

which is the first section of my counterliminary reduction of thetemperature of the air and for freezing out any remaining moisturetherein. It consists of the usual w appliances used in mechanicalrefrigeration,

: ing drum 16, as shown,

namely, sor 17, livering a high -pressure CO gas compresconnectingdischarge pipe 18 deto the water-cooled condenser 19,

liquid CO. reservoir 20, liquid discharge pipe 21, and li uid COpressure-releasing valve 22. The 0 released liquid is thence deliveredto the vaporizing ,pipe 23 and triple upwardly-delivering helical coils24. Th vaporizing liquid or CO gas then passes to the vreturn pipe 25,and is thence delivered to the compressor where it is recompressed. Byconstruction of the freeza helical passage 26 is formed between the COcopper coils (24) through which the compressed air from pipe 15 ispassed down through the drum and upwardly into the inner conduit 27. Inthis way contrary the compressed air passes in a izing CO gas in theexpansion pipe 23 and .vaporizing coils 24. A temperature of 30 to 40?.below zero, Fahrenheit, can easily be maintained in the drum (-16), sothat the compressed air as it leaves the drum by is at a temperature ofabout -36 F.

Any frost or ice in the compressed air coils 13 or on the outside of theCO; pipes 23 and 24 may be easily melted by closing ailr valves 29, 30and 31, and opening air valve 32 andpartially opening the drip cook 33;then by shutting 'ofl' the water to v the cooler 2 the' compressor willdeliver hot throng calcium chlorid and caustic air to the air coilsl3and drum 16, without passing it through the purifying drums and 10. Thewater'may be drawn off and 3 are drip cooks for lime barrel and potashdrums,

respectively.

Having thoroughly dried and purified the direction to the flow of thevapor-.

free of moisture, and

sorbed b drip cocks- 33 and34 At 35, 36

compressed air, it 15 now passed to the main counter-current thermalinterchanger and submerged liquefier, from pipe 28 (see Figs. 1 and 2).I make the interchanger prefably, of a triple'helical descending coppercoil 38 around the hollow core 38, and in closed in the double-walledconduit 39 and 39, which allows or forms the expanded air or vaporreturn-flow or counter-current helical passage 40 between the coils 38.The

air low-pressure evaporating holder, which incloses the condenser andits liquefying .coil.v This evaporating holder is insulated by thevacuum 47, held by the outer rigid case or barrel 48. I allow the sheetmetal which forms the liquid-air vessel 46 to pass around and inclosethe barrel 48 as shown being connected therewith at 49, thus forming acomplete air-tight inclosure. I pump the air out of the space 47,through the aperture 50, and then fill the space with CO gas, and sealup the aperture 50 with the cap 51. At 52 I have an overflow outlet tovessel 46, controlled by the valve 53 which is operated by the handwheel 54; this outlet has a movable outer elbow or spout 55, which maybe turned upward as shown by the dotted lines 56, and used as a fillingspout to fill the evaporating vessel 46 with an initial charge of liquidair from an outside source.

At 57 I have an annular cup or catch around'the outside of the'vessel46,'near the bottom; and at 58 I show a Wire gauze cap or cup fittedover the outside of the lower end of the vessel 46, which is filled withcharcoal.

tle evaporating holder 46 from outside heat. I

there should be any traces of air in the CO gas in the space 47, thiswill be quickly ahthe charcoal in the gauze cup 58, as this 0 arcoal isheld close to the coldest surface of the vessel 46, and charcoal when atthe low temperature of liquid air has great power of absorbing gaseousair. I am thus particular'in formin the vacuum insulation around theevaporating holder 46,

tween the walls 39 and 39 of the conduit which incloses the same.

The vapor or expanded air helical passage 40 deliVers to the pipe 61(see Figs. 2 and 1) which delivers to the low-pressure helical passage40', in the pre-cooler 24 (see 1), and thence to the air-expanded pipeHere it may be discharged to the outer atmosphere through check valve62, by closing valve 63; or it may be returned to the compressor andre-compressed by opening valve 63. It will thus be noticed that I makeuse of the cold expanded air before it is finally discharged, to coolthe compressed air somewhat before it'is passed into the CO5refrigerating drum 16. In this waythe expanded air is finally dischargedor re, turned to the compressor, at practically the same temperature ofthe air as it leaves the purifying drums 7 and 10, or at about F.; andwhatever cooling is obtained from the CO freezing drum (16) is a cleargain,'and serves not only to freeze out the last traces of moisture fromthe compressed air, but also to off-set any thermal gains of the systemby reason of imperfect insulation..

As the air in the supply coils 38 and the condenser 42 and theair-liquefying coil 42, (see Fig. 2) is maintained at a compressionsubstantially at or above its critical pressure, it will liquefy at 220F.; and as, when at thatpressure and at that temperature, its density asa gas is identical with it density as a liquid, it then passes to aliqui instantaneously, if its temperature is lowered in the slightestdegree, if the pressure be maintained at or above '39 atmospheres. The

liquid air in the evaporating holder 46, be-

ing at substantially atmospheric pressure, its temperature ismaintainedat about 313 or 93 degrees colder than the liquefying point of thecooled compressed air in the submerged drum 42 and submerged coils 42.

At 65 I show an air-expansion valve, generally for use only in startingup, when an initial charge of liquid air for the evaporat; ing vessel 46is not obtainable; it is located above the condenser 42, or between itand the compressed-air supply, and is operated by the outside hand wheel66 and discharges through the perforated expansion head 67. By openingthis valve (65) a trifle, it acts as a throttled orifice or porous-plug,and the compressed air in pipes 38, (at 45 to 50 atmospheres tension) isreleased or let down to substantially atmospheric pressure in the head67 after it has passed through said valve; and in thus being released itdrops in temperature in accordance with the wellknown formula of theso-called Joule- Thomson effect. The cooled expanded air is conductedback through said conduit (39) in the helical passage 40 and 40 over thecompressed air supply pipes 38that which liquefies dropping by gravityinto the vessel 46.v The air in these pipes and in condenser 42 and 42'is maintained at full pressure,the opening of the valve 65 not being sogreat as to reduce the pressure. As soon as the holder 46 is. filledwith a liquid-air charge,--valve 65 may be closed and its further usedispensed with, if preferred.

An important and novel feature of my invention is the location of theliquefier proper or high-pressure condenser 42 and coil 42' within theliquid air vessel or holder 46; and making of that condenser a closeddrum, as it were, so that only compressed air of high tension (to orabove its critical pressure) fills it, and without current or flowtherein,

as all the air'supplied to it becomes liquefied; therefore the onlydelivery of compressed air thereto is to take the place of that whichhas. become liquefied therein while at substantially its criticalpressure; and no air can escape therefrom until after it is liquefiedbut only liquid air throughcharges, intermittently, or it may be ,dis-

charged continuously before it entirely fills the condenser 42.

As has been indicated above, the air expansion valve shown at 65 may bekept 7 open during the operation of the apparatus.

When this is the case it willlbe noticed-that the incoming compressedair delivered to coils .38: (Fig; 2), as subjected tothe cumulativerefrigerative effect of the vapors from the evaporating liquefied gasesin the lowpressure evaporating vessel 46, reinforced or augmented by thecold gases expanding from the throttled valve 65 and expansion head 67as said vapors and'unliquefied.

gases pass up through said helical passage 40, will grow colder andcolder as it passes down through the coils 38 in a contrary direction sothat there will be-partial liquefaction, leaving an unliquefied portionto be released from pressure and expanded through the throttle 65 andexpansion head 67.

The apparatus which illustrates my process and which accompanies thisspecification, as may readily .be seen, is especially adapted to bringabout the change, as above noted, of partial liquefaction; for byadjusting the valves 43 and 65 any desired proportion of the liquefiedor unliquefied gases may be released. The amount of air passed throughthese valves will govern the temperature in coils 38 and consequentlythe amount of air liquefied therein. The location of the expansion valve65 at the lower end of the liquefying coils 38 or between that lower endand the submerged receiver 42, is just at the point required to take theunliquefied portion which is left in the coils 38 (or' in the receiver42) when used as a liquefying condenser and by releasing from pressure,expand the same.

By my process, as herewith illustrated, the

\ resulting liquid in the low pressure evaporating vessel 46, as drawnoff finally through valve 53, will be almost pure oxygen liquid.

The vapors from the evaporating vessel 46 will come in contact and mixwith the ex .panded gaseous residue from the expansion head 67 and byrectification and thermal inter-action between the two the oxygen gas inthe vapors'will become condensed and colhot in the vessel 46 while theunli'quefied portion, principally nitrogen,

the helical will pass through passageway and out through the pipe 61.

If during the operationof the apparatus check valve 62 (see Fig. 1) iskept open and valve 63 -is kept closed, my apparatus in liquefying willalso partially separate the two ases, oxygen and nitrogen, (owing to the'fference' in temperature of their boiling points) by fractionalevaporation of the liquefied air in the 'lowepressure holder 46;

andconsequentlythe overflow liquid drawn from the apparatus throughdischarge tube 52 will be very rich in oxygen, and the return flow ofexpanded gas or air. leaving the method of operating, the liquefiedairin the high-pressure subdown from 220 system through ingly rich innitrogen. i *If the liquefied air in the high-pressure condenser 42 or42- is discharged therefrom a; soon as condensed, then the latent heat-o vaporization required, as released from pressure, would naturally beabsorbed from the l1qu1d itself,'unti l its temperature falls toitsboiling point313-F. The preferred however, is to allow mergedcondenserf42 to remain therein until it Is sub-cooled, .or cooled afterliquefaction, F., to 312.6 F., the

' temperature of the liquid surrounding the condenser in the insulatedevaporating vessel air in the condenser 42 released from pressure anddelivered to the evaporating vessel 46, will already be at thetemperature in such vessel, and will not vaporize on being released.

Fractional evaporation of the liquid in the holder 46 will then go oncontinuously,

valve 62 will be correspond.

for the difference in temperature between the evaporating liquid in theholder 46 and the liquefying point of the cooled compressed air (40 to45 atmospheres) in the condenser 42, is 90 degrees Fahrenheit; thelatent heat, now at its maximum, being drawn entirely from both thecooled compressed air and the liquefied air in the condenser 42 and42rapidly liquefying the compressed. air therein (without reduction ofpressure) and sub-cooling the liquid as fast as produced. All of thevapor from the evaporated liquid in the. holder 46, at sub ing theoperation ofthe apparatus, the surplus, or overflow alone being drawnfrom' the reservoir. This surplus or output of liquid, by reason of thehigh-pressure submerged liquefier herein shown, and other .valuablefeatures herein described, will be much more than heretofore obtainedfor the energy expended in this class of. air-liquefying'apparatus, orabout 50% of all the air treated.

I am aware that compressed air has been liquefied by subjecting the sameto the cool- 'ingaction of liquid air, for instance, as

shown 1n my U. S: Patent No. 666,693; but I knowof no case in which airhas been thus liquefied while compressed to a tension to or abovesubstantially its criticalpressure. In all such cases where air has beenliquefied by liquid air, the object sought has been not liquefaction butseparation, and neither utilization of nor reference has been made totheprinciple or physical law involved in this invention, that airlique-. fies at its critical point (or junction of critical pressure andcritical temperature) without giving out practically any latent heat ofcondensation; and that whenliquid air evaporates at substantiallyatmospheric pressure it requires a large amount of latent heat, or about120 B. T. U. per pound. This principle or irrefutable law,

faction of all gases, I utilize by my improved art or process hereinfor'liquefying am v 7 Having thus described my invention, what whichgoverns the vaporization of alll'iquids and the lique- I claim as newand original and desire to secure by Letters l'atent, is

1. The art or process of liquefying atmospheric air consisting of orincluding the compressing of air substantially to or above normaltemperature; 2nd, to the refrigerasion of increasingly refrigerativeactions.

1st, to the cooling action of a counter-current of low-pressure expandedair below the tive effect of aliquefied gas released from pressure andevaporated; 3rd, to the cooling action of a counter-current of the vaporand cold expanding gases evaporated from liquid air of substantiallyatmospheric'pressure; and 4th, to' the cooling of said low-pressure'evaporatlng liquid air thereby liquefying said cooled compressed airwhile at substantially its. critical pressuresure; 2nd, to acounter-current of evaporating and evaporated liquefied gas released asa liquid from a constant relatively high to a constant relatively lowpressure; and 3rd,

to a combined counter-current of said expanded gases as released frompressure, and.

of the vapor and cold expanding gases evaporated from said liquid air ofsubstantially atmospheric pressure.

3. In the art or process of liquefying atmospheric air, the method ofcooling a moving column of compressed air which consists, successivelyof1st cooling it by'a counter-v current of low pressure expanded airpreviously released as a gas from said compressed air column, but not.as cold as when released; 2nd, in cooling it by a colder counter-currentof evaporating liquefied gas released from pressure;'and 3rd, in coolingit by a lowpressure counter-current of still colder expanded air,released from said cooled compressed air columnall of saidcounter-currents being conducted in juxtaposition with said movingcolumn of compressed air, but in an opposite direction thereto.

4. The art or process of liquefying atmos- ,pheric air, which comprisescompressing .the

air and cooling the same; liquefying a portion thereof while under saidcompression, and sub-cooling the same in avessel or conduit submerged inorin contact with liquid.

air of substantially atmospheric pressurethereby causing partialfractional evaporation thereof by heat derived from said highpressureliquid being cooled; releasing the action direct pressure and thatportion of the gaseous residue liquefied as released from pressure.

5. The art or process of liquefying atmospheric air, which comprisescompressing the air; liquefying a portion thereof while under saidcompression, and releasing the gaseous residue from pressure, expandingthe same, and liquefying as released a portion of the same atsubstantially atmospheric pressure; and finally subjecting both liquidsto fractional evaporation, and utilizing the vapors therefrom to coolcompressed air about to be liquefied.

6. The art or process of liquefying atmospheric air,which comprisescompressing the air; liquefying a portion thereof While under saidcompression, and releasing the gaseous residue from pressure, expandingthe same and liquefying as released a portion of the same atsubstantially atmospheric pressure; and finally subjecting both liquidsto 1 vfractional evaporation and utilizing the vapors therefrom, and thesaid unliquefied gaseous residue to cool compressed air about to beliquefied.

'7. The process of liquefying air and sepa-- rating the same into itsconstituents, oxygen and nitrogen, which comprises compressing the airand cooling the same; partially liquefying the same while compressed, andseparating the liquid thus obtained from the gaseous residue bydelivering the same to a high-pressure condenser or receiver submergedin liquid air of substantially atmospheric pressure in a low-pressureevaporating vessel; expanding saidgaseous residue through a throttledvalve and thereby liquefying a portion of said gaseous residue un-1 derthe Joule-Thomson efiect, and delivering the same to said low-pressurevessel; and finally replenishing the liquid evaporating in saidlow-pressure vessel by releasing from pressure and delivering to saidvessel the liquid in said high pressure submerged condenser.

8. The process of liquefying. air and separating the same into itsconstituents, oxygen and nitrogen, which comprises compressing the airand cooling the same; liquefying portions thereof while compressed, andseparat-v ing the liquid thus obtained from the gaseous residue bydelivering the same to a high pressure condenser or receiversubmerged inliquid air of substantially atmospheric pres sure in a low-pressureevaporating vessel; expanding said gaseous residue through a throttledvalve and thereby liquefying a portion of said gaseous residue under theJoule-Thomson efiect, and delivering same to said low-pressure vessel;and finally-replenishing the liquid evaporating in said low pressurevessel by releasing from ressure and delivering to said vessel theliquid in said high-pressure submerged condenserboth the cold vaporsfrom said evaporating Vessel, and the cold unliquefied'gases from saidthrottled valve, being utilized to cool the incoming supply ofcompressed air.

Signed at New York, in the county of New York and State of New York,this 30th 1 J day of October, A. D. 1907.

JAMES PLAC I Witnesses 2 JOHN H. AGKROYD, J. G. GADsDEN.

